A variety of products can be made from thermoplastic and/or thermoset materials. Some thermoplastic and thermoset materials are relatively expensive or have limited performance characteristics or physical properties that are lacking. Some elastomers, such as virgin rubber or scrap rubber, may be less expensive or have desirable performance characteristics or desirable physical properties.
A typical passenger car tire is a complex manufactured article which typically comprises, as major constituents, synthetic rubber, natural rubber, carbon black, steel, as well as lesser quantities of fabrics, filler accelerators, antiozonants etc. These constituents are not uniformly distributed throughout the tire but occur in varying concentrations at differing locations in the tire. For example, the tread, base, sidewall and inner liner of the tire are comprised of varying proportions of natural rubber, styrene-butadiene rubber and isobutylene-isoprene rubber. Typical mechanical processes, such as used to reduce the tires to small fragmentary particles for further processing to enable reclamation of the chemical value of the tire include granulation, comminution, cutting, sonic impacting or cryogenic fragmentation. These processes may be non-selective and thus the rubber particles may originate from all regions of the tire and thus the rubber particles so obtained may be of varying composition. While the fabric and steel content may be separated using well-known techniques, it is difficult or impossible to economically separate the rubber constituents. Thus processes which seek to extract value from these rubber particles should have comprehensive utility and yield acceptable products irrespective of the source location of the rubber particles in the tire.
Various processes and systems for treating particulate rubber and/or for utilizing particulate rubber as an addition to thermoplastic or thermoset polymers have been proposed. For example, U.S. Pat. Nos. 5,488,080; 5,604,277; 6,310,126; 6,346,561; and 6,527,430 to Osborn, and U.S. Patent Publication Nos. 2001/0004649 and 2003/0204002 to Osborn disclose such processes and systems. Other disclosures include U.S. Pat. Nos. 3,873,482; 4,244,841; 4,481,335; 4,579,871; 4,792,589; 4,895,911; 6,924,319; 6,924,320; and 7,342,052. All of these patents and applications are incorporated herein by reference.
Despite numerous attempts to successfully treat particulate rubber and to mix such treated rubber with thermoplastic or thermoset polymers, a need still exists for a process and system for making improved materials.